With the current interest in walking as a form of exercise, attention has been directed to the biomechanics of walking and the need to design shoes to accommodate stresses developed during walking. Although walking causes less stress on a person's foot and leg than running, there are, nonetheless, sufficient forces occurring particularly during long walks, to cause a person to become tired or perhaps even cause foot injuries.
Problems relating to walking for exercise center on the biodynamics involved. As a person walks, the outside heel strikes the ground first, causing the foot to assume a supernated position. The foot then rolls inwardly, pronating to a maximum position, before rolling outwardly again and supernating as it leaves the ground. Pronation occurs to varying degrees with every person. A limited amount of pronation does not ordinarily present a problem. However, injuries and excessive weariness will occur when there is excessive pronation. For that reason, there is a need for footwear that tends to limit the amount of pronation.
Another concern in designing walking shoes relates to vertical ground reaction forces. These forces develop between the foot and the ground each time the foot strikes the ground. While these forces are no more than one to one and a half times body weight when walking, as compared with three times body weight when running, the walking forces are applied over a longer period of time, because walking is a slower activity than running. For these reasons, less cushioning material is ordinarily needed for walking shoes than for running or aerobic shoes. In fact, walkers using running shoes may experience instability or discomfort because of excessive cushioning material.
The forces of walking also relate to the characteristics of pressure distribution patterns of the foot. In walking, the pressure distribution patterns starts with pressure at the rear heel area, then the mid foot or instep region, and finally under the metatarsal heads or ball of the foot. Thus, high forced distribution occurs under the heel, ball and first toe. A proper walking shoe must accordingly, reduce these forces by distributing them to other portions of the foot.
Another characteristic of walking is the dynamics that relate to the mid-foot area of the foot. Unlike running, the foot does not assume a rigid lever like system because of lower forces inherent in the walking motion. Thus, the intrinsic muscles of the foot must work harder to pull the foot bones together. Therefore, a properly designed walking shoe demands a snug support for the foot arch to avoid foot fatigue of the instep.
These biomechanical characteristics, including rear foot motion pattern, vertical ground reaction forces, pressure distribution patterns, and mid-foot dynamics are different in walking than running or other sports. It is these characteristics which require specific consideration in designing a walking shoe.